inode.c

嵌入式系统设计与实例开发实验教材二源码 多线程应用程序设计 串行端口程序设计 AD接口实验 CAN总线通信实验 GPS通信实验 Linux内核移植与编译实验 IC卡读写实验 SD驱动使

	read_inode:	make_bad_inode,
	fh_to_dentry:	fat_fh_to_dentry,
	dentry_to_fh:	fat_dentry_to_fh,
};

/*
 * Read the super block of an MS-DOS FS.
 *
 * Note that this may be called from vfat_read_super
 * with some fields already initialized.
 */
struct super_block *
fat_read_super(struct super_block *sb, void *data, int silent,
		struct inode_operations *fs_dir_inode_ops)
{
	struct inode *root_inode;
	struct buffer_head *bh;
	struct fat_boot_sector *b;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	char *p;
	int logical_sector_size, hard_blksize, fat_clusters = 0;
	unsigned int total_sectors, rootdir_sectors;
	int fat32, debug, error, fat, cp;
	struct fat_mount_options opts;
	char buf[50];
	int i;
	char cvf_format[21];
	char cvf_options[101];

	cvf_format[0] = '\0';
	cvf_options[0] = '\0';
	sbi->cvf_format = NULL;
	sbi->private_data = NULL;

	sbi->dir_ops = fs_dir_inode_ops;

	sb->s_maxbytes = MAX_NON_LFS;
	sb->s_op = &fat_sops;

	hard_blksize = get_hardsect_size(sb->s_dev);
	if (!hard_blksize)
		hard_blksize = 512;

	opts.isvfat = sbi->options.isvfat;
	if (!parse_options((char *) data, &fat, &debug, &opts,
			   cvf_format, cvf_options))
		goto out_fail;
	/* N.B. we should parse directly into the sb structure */
	memcpy(&(sbi->options), &opts, sizeof(struct fat_mount_options));

	fat_cache_init();

	sb->s_blocksize = hard_blksize;
	set_blocksize(sb->s_dev, hard_blksize);
	bh = sb_bread(sb, 0);
	if (bh == NULL) {
		printk("FAT: unable to read boot sector\n");
		goto out_fail;
	}

/*
 * The DOS3 partition size limit is *not* 32M as many people think.  
 * Instead, it is 64K sectors (with the usual sector size being
 * 512 bytes, leading to a 32M limit).
 * 
 * DOS 3 partition managers got around this problem by faking a 
 * larger sector size, ie treating multiple physical sectors as 
 * a single logical sector.
 * 
 * We can accommodate this scheme by adjusting our cluster size,
 * fat_start, and data_start by an appropriate value.
 *
 * (by Drew Eckhardt)
 */


	b = (struct fat_boot_sector *) bh->b_data;
	logical_sector_size =
		CF_LE_W(get_unaligned((unsigned short *) &b->sector_size));
	if (!logical_sector_size
	    || (logical_sector_size & (logical_sector_size - 1))) {
		printk("FAT: bogus logical sector size %d\n",
		       logical_sector_size);
		brelse(bh);
		goto out_invalid;
	}

	sbi->cluster_size = b->cluster_size;
	if (!sbi->cluster_size
	    || (sbi->cluster_size & (sbi->cluster_size - 1))) {
		printk("FAT: bogus cluster size %d\n", sbi->cluster_size);
		brelse(bh);
		goto out_invalid;
	}

	if (logical_sector_size < hard_blksize) {
		printk("FAT: logical sector size too small for device"
		       " (logical sector size = %d)\n", logical_sector_size);
		brelse(bh);
		goto out_invalid;
	}

	sbi->cluster_bits = ffs(logical_sector_size * sbi->cluster_size) - 1;
	sbi->fats = b->fats;
	sbi->fat_start = CF_LE_W(b->reserved);
	if (!b->fat_length && b->fat32_length) {
		struct fat_boot_fsinfo *fsinfo;
		struct buffer_head *fsinfo_bh;
		int fsinfo_block, fsinfo_offset;

		/* Must be FAT32 */
		fat32 = 1;
		sbi->fat_length = CF_LE_L(b->fat32_length);
		sbi->root_cluster = CF_LE_L(b->root_cluster);

		sbi->fsinfo_sector = CF_LE_W(b->info_sector);
		/* MC - if info_sector is 0, don't multiply by 0 */
		if (sbi->fsinfo_sector == 0)
			sbi->fsinfo_sector = 1;

		fsinfo_block =
			(sbi->fsinfo_sector * logical_sector_size) / hard_blksize;
		fsinfo_offset =
			(sbi->fsinfo_sector * logical_sector_size) % hard_blksize;
		fsinfo_bh = bh;
		if (fsinfo_block != 0) {
			fsinfo_bh = sb_bread(sb, fsinfo_block);
			if (fsinfo_bh == NULL) {
				printk("FAT: bread failed, FSINFO block"
				       " (blocknr = %d)\n", fsinfo_block);
				brelse(bh);
				goto out_invalid;
			}
		}
		fsinfo = (struct fat_boot_fsinfo *)&fsinfo_bh->b_data[fsinfo_offset];
		if (!IS_FSINFO(fsinfo)) {
			printk("FAT: Did not find valid FSINFO signature.\n"
			       "Found signature1 0x%x signature2 0x%x sector=%ld.\n",
			       CF_LE_L(fsinfo->signature1),
			       CF_LE_L(fsinfo->signature2),
			       sbi->fsinfo_sector);
		} else {
			sbi->free_clusters = CF_LE_L(fsinfo->free_clusters);
		}

		if (fsinfo_block != 0)
			brelse(fsinfo_bh);
	} else {
		fat32 = 0;
		sbi->fat_length = CF_LE_W(b->fat_length);
		sbi->root_cluster = 0;
		sbi->free_clusters = -1; /* Don't know yet */
	}

	sbi->dir_per_block = logical_sector_size / sizeof(struct msdos_dir_entry);
	sbi->dir_per_block_bits = ffs(sbi->dir_per_block) - 1;

	sbi->dir_start = sbi->fat_start + sbi->fats * sbi->fat_length;
	sbi->dir_entries =
		CF_LE_W(get_unaligned((unsigned short *)&b->dir_entries));
	rootdir_sectors = sbi->dir_entries
		* sizeof(struct msdos_dir_entry) / logical_sector_size;
	sbi->data_start = sbi->dir_start + rootdir_sectors;
	total_sectors = CF_LE_W(get_unaligned((unsigned short *)&b->sectors));
	if (total_sectors == 0)
		total_sectors = CF_LE_L(b->total_sect);
	sbi->clusters = (total_sectors - sbi->data_start) / sbi->cluster_size;

	error = 0;
	if (!error) {
		sbi->fat_bits = fat32 ? 32 :
			(fat ? fat :
			 (sbi->clusters > MSDOS_FAT12 ? 16 : 12));
		fat_clusters =
			sbi->fat_length * logical_sector_size * 8 / sbi->fat_bits;
		error = !sbi->fats || (sbi->dir_entries & (sbi->dir_per_block - 1))
			|| sbi->clusters + 2 > fat_clusters + MSDOS_MAX_EXTRA
			|| logical_sector_size < 512
			|| PAGE_CACHE_SIZE < logical_sector_size
			|| !b->secs_track || !b->heads;
	}
	brelse(bh);

	if (error)
		goto out_invalid;

	sb->s_blocksize = logical_sector_size;
	sb->s_blocksize_bits = ffs(logical_sector_size) - 1;
	set_blocksize(sb->s_dev, sb->s_blocksize);
	sbi->cvf_format = &default_cvf;
	if (!strcmp(cvf_format, "none"))
		i = -1;
	else
		i = detect_cvf(sb,cvf_format);
	if (i >= 0)
		error = cvf_formats[i]->mount_cvf(sb, cvf_options);
	if (error || debug) {
		/* The MSDOS_CAN_BMAP is obsolete, but left just to remember */
		printk("[MS-DOS FS Rel. 12,FAT %d,check=%c,conv=%c,"
		       "uid=%d,gid=%d,umask=%03o%s]\n",
		       sbi->fat_bits,opts.name_check,
		       opts.conversion,opts.fs_uid,opts.fs_gid,opts.fs_umask,
		       MSDOS_CAN_BMAP(sbi) ? ",bmap" : "");
		printk("[me=0x%x,cs=%d,#f=%d,fs=%d,fl=%ld,ds=%ld,de=%d,data=%ld,"
		       "se=%u,ts=%u,ls=%d,rc=%ld,fc=%u]\n",
		       b->media, sbi->cluster_size, sbi->fats,
		       sbi->fat_start, sbi->fat_length, sbi->dir_start,
		       sbi->dir_entries, sbi->data_start,
		       CF_LE_W(get_unaligned((unsigned short *)&b->sectors)),
		       CF_LE_L(b->total_sect), logical_sector_size,
		       sbi->root_cluster, sbi->free_clusters);
		printk ("hard sector size = %d\n", hard_blksize);
	}
	if (i < 0)
		if (sbi->clusters + 2 > fat_clusters)
			sbi->clusters = fat_clusters - 2;
	if (error)
		goto out_invalid;

	sb->s_magic = MSDOS_SUPER_MAGIC;
	/* set up enough so that it can read an inode */
	init_MUTEX(&sbi->fat_lock);
	sbi->prev_free = 0;

	cp = opts.codepage ? opts.codepage : 437;
	sprintf(buf, "cp%d", cp);
	sbi->nls_disk = load_nls(buf);
	if (! sbi->nls_disk) {
		/* Fail only if explicit charset specified */
		if (opts.codepage != 0)
			goto out_fail;
		sbi->options.codepage = 0; /* already 0?? */
		sbi->nls_disk = load_nls_default();
	}

	sbi->nls_io = NULL;
	if (sbi->options.isvfat && !opts.utf8) {
		p = opts.iocharset ? opts.iocharset : CONFIG_NLS_DEFAULT;
		sbi->nls_io = load_nls(p);
		if (! sbi->nls_io)
			/* Fail only if explicit charset specified */
			if (opts.iocharset)
				goto out_unload_nls;
	}
	if (! sbi->nls_io)
		sbi->nls_io = load_nls_default();

	root_inode = new_inode(sb);
	if (!root_inode)
		goto out_unload_nls;
	root_inode->i_ino = MSDOS_ROOT_INO;
	fat_read_root(root_inode);
	insert_inode_hash(root_inode);
	sb->s_root = d_alloc_root(root_inode);
	if (!sb->s_root)
		goto out_no_root;
	if(i >= 0) {
		sbi->cvf_format = cvf_formats[i];
		++cvf_format_use_count[i];
	}
	return sb;

out_no_root:
	printk("FAT: get root inode failed\n");
	iput(root_inode);
	unload_nls(sbi->nls_io);
out_unload_nls:
	unload_nls(sbi->nls_disk);
	goto out_fail;
out_invalid:
	if (!silent) {
		printk("VFS: Can't find a valid FAT filesystem on dev %s.\n",
			kdevname(sb->s_dev));
	}
out_fail:
	if (opts.iocharset) {
		printk("FAT: freeing iocharset=%s\n", opts.iocharset);
		kfree(opts.iocharset);
	}
	if(sbi->private_data)
		kfree(sbi->private_data);
	sbi->private_data = NULL;
 
	return NULL;
}

int fat_statfs(struct super_block *sb,struct statfs *buf)
{
	int free,nr;
       
	if (MSDOS_SB(sb)->cvf_format &&
	    MSDOS_SB(sb)->cvf_format->cvf_statfs)
		return MSDOS_SB(sb)->cvf_format->cvf_statfs(sb,buf,
						sizeof(struct statfs));
	  
	lock_fat(sb);
	if (MSDOS_SB(sb)->free_clusters != -1)
		free = MSDOS_SB(sb)->free_clusters;
	else {
		free = 0;
		for (nr = 2; nr < MSDOS_SB(sb)->clusters+2; nr++)
			if (!fat_access(sb,nr,-1)) free++;
		MSDOS_SB(sb)->free_clusters = free;
	}
	unlock_fat(sb);
	buf->f_type = sb->s_magic;
	buf->f_bsize = 1 << MSDOS_SB(sb)->cluster_bits;
	buf->f_blocks = MSDOS_SB(sb)->clusters;
	buf->f_bfree = free;
	buf->f_bavail = free;
	buf->f_namelen = MSDOS_SB(sb)->options.isvfat ? 260 : 12;
	return 0;
}

static int is_exec(char *extension)
{
	char *exe_extensions = "EXECOMBAT", *walk;

	for (walk = exe_extensions; *walk; walk += 3)
		if (!strncmp(extension, walk, 3))
			return 1;
	return 0;
}

static int fat_writepage(struct page *page)
{
	return block_write_full_page(page,fat_get_block);
}
static int fat_readpage(struct file *file, struct page *page)
{
	return block_read_full_page(page,fat_get_block);
}
static int fat_prepare_write(struct file *file, struct page *page, unsigned from, unsigned to)
{
	return cont_prepare_write(page,from,to,fat_get_block,
		&MSDOS_I(page->mapping->host)->mmu_private);
}
static int _fat_bmap(struct address_space *mapping, long block)
{
	return generic_block_bmap(mapping,block,fat_get_block);
}
static struct address_space_operations fat_aops = {
	readpage: fat_readpage,
	writepage: fat_writepage,
	sync_page: block_sync_page,
	prepare_write: fat_prepare_write,
	commit_write: generic_commit_write,
	bmap: _fat_bmap
};

/* doesn't deal with root inode */
static void fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
{
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	int nr;

	INIT_LIST_HEAD(&MSDOS_I(inode)->i_fat_hash);
	MSDOS_I(inode)->i_location = 0;
	MSDOS_I(inode)->i_fat_inode = inode;
	inode->i_uid = sbi->options.fs_uid;
	inode->i_gid = sbi->options.fs_gid;
	inode->i_version = ++event;
	inode->i_generation = CURRENT_TIME;
	
	if ((de->attr & ATTR_DIR) && !IS_FREE(de->name)) {
		inode->i_generation &= ~1;
		inode->i_mode = MSDOS_MKMODE(de->attr,S_IRWXUGO &
		    ~sbi->options.fs_umask) | S_IFDIR;
		inode->i_op = sbi->dir_ops;
		inode->i_fop = &fat_dir_operations;

		MSDOS_I(inode)->i_start = CF_LE_W(de->start);
		if (sbi->fat_bits == 32) {
			MSDOS_I(inode)->i_start |=
				(CF_LE_W(de->starthi) << 16);
		}
		MSDOS_I(inode)->i_logstart = MSDOS_I(inode)->i_start;
		inode->i_nlink = fat_subdirs(inode);
		    /* includes .., compensating for "self" */
#ifdef DEBUG
		if (!inode->i_nlink) {
			printk("directory %d: i_nlink == 0\n",inode->i_ino);
			inode->i_nlink = 1;
		}
#endif
		if ((nr = MSDOS_I(inode)->i_start) != 0)
			while (nr != -1) {
				inode->i_size += 1 << sbi->cluster_bits;
				if (!(nr = fat_access(sb, nr, -1))) {
					printk("Directory %ld: bad FAT\n",
					    inode->i_ino);
					break;
				}
			}
		MSDOS_I(inode)->mmu_private = inode->i_size;
	} else { /* not a directory */
		inode->i_generation |= 1;
		inode->i_mode = MSDOS_MKMODE(de->attr,
		    ((sbi->options.showexec &&
		       !is_exec(de->ext))
		    	? S_IRUGO|S_IWUGO : S_IRWXUGO)
		    & ~sbi->options.fs_umask) | S_IFREG;
		MSDOS_I(inode)->i_start = CF_LE_W(de->start);
		if (sbi->fat_bits == 32) {
			MSDOS_I(inode)->i_start |=
				(CF_LE_W(de->starthi) << 16);
		}
		MSDOS_I(inode)->i_logstart = MSDOS_I(inode)->i_start;
		inode->i_size = CF_LE_L(de->size);
	        inode->i_op = &fat_file_inode_operations;
	        inode->i_fop = &fat_file_operations;
		inode->i_mapping->a_ops = &fat_aops;
		MSDOS_I(inode)->mmu_private = inode->i_size;
	}
	if(de->attr & ATTR_SYS)
		if (sbi->options.sys_immutable)
			inode->i_flags |= S_IMMUTABLE;
	MSDOS_I(inode)->i_attrs = de->attr & ATTR_UNUSED;
	/* this is as close to the truth as we can get ... */
	inode->i_blksize = 1 << sbi->cluster_bits;
	inode->i_blocks = ((inode->i_size + inode->i_blksize - 1)
			   & ~(inode->i_blksize - 1)) >> 9;
	inode->i_mtime = inode->i_atime =
		date_dos2unix(CF_LE_W(de->time),CF_LE_W(de->date));
	inode->i_ctime =
		MSDOS_SB(sb)->options.isvfat
		? date_dos2unix(CF_LE_W(de->ctime),CF_LE_W(de->cdate))
		: inode->i_mtime;
	MSDOS_I(inode)->i_ctime_ms = de->ctime_ms;
}

void fat_write_inode(struct inode *inode, int wait)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *bh;
	struct msdos_dir_entry *raw_entry;
	unsigned int i_pos;

retry:
	i_pos = MSDOS_I(inode)->i_location;
	if (inode->i_ino == MSDOS_ROOT_INO || !i_pos) {
		return;
	}
	lock_kernel();
	if (!(bh = fat_bread(sb, i_pos >> MSDOS_SB(sb)->dir_per_block_bits))) {
		printk("dev = %s, ino = %d\n", kdevname(inode->i_dev), i_pos);
		fat_fs_panic(sb, "msdos_write_inode: unable to read i-node block");
		unlock_kernel();
		return;
	}
	spin_lock(&fat_inode_lock);
	if (i_pos != MSDOS_I(inode)->i_location) {
		spin_unlock(&fat_inode_lock);
		fat_brelse(sb, bh);
		unlock_kernel();
		goto retry;
	}

	raw_entry = &((struct msdos_dir_entry *) (bh->b_data))
	    [i_pos & (MSDOS_SB(sb)->dir_per_block - 1)];
	if (S_ISDIR(inode->i_mode)) {
		raw_entry->attr = ATTR_DIR;
		raw_entry->size = 0;
	}
	else {
		raw_entry->attr = ATTR_NONE;
		raw_entry->size = CT_LE_L(inode->i_size);
	}
	raw_entry->attr |= MSDOS_MKATTR(inode->i_mode) |
	    MSDOS_I(inode)->i_attrs;
	raw_entry->start = CT_LE_W(MSDOS_I(inode)->i_logstart);
	raw_entry->starthi = CT_LE_W(MSDOS_I(inode)->i_logstart >> 16);
	fat_date_unix2dos(inode->i_mtime,&raw_entry->time,&raw_entry->date);
	raw_entry->time = CT_LE_W(raw_entry->time);
	raw_entry->date = CT_LE_W(raw_entry->date);
	if (MSDOS_SB(sb)->options.isvfat) {
		fat_date_unix2dos(inode->i_ctime,&raw_entry->ctime,&raw_entry->cdate);
		raw_entry->ctime_ms = MSDOS_I(inode)->i_ctime_ms;
		raw_entry->ctime = CT_LE_W(raw_entry->ctime);
		raw_entry->cdate = CT_LE_W(raw_entry->cdate);
	}
	spin_unlock(&fat_inode_lock);
	fat_mark_buffer_dirty(sb, bh);
	fat_brelse(sb, bh);
	unlock_kernel();
}


int fat_notify_change(struct dentry * dentry, struct iattr * attr)
{
	struct super_block *sb = dentry->d_sb;
	struct inode *inode = dentry->d_inode;
	int error;

	/* FAT cannot truncate to a longer file */
	if (attr->ia_valid & ATTR_SIZE) {
		if (attr->ia_size > inode->i_size)
			return -EPERM;
	}

	error = inode_change_ok(inode, attr);
	if (error)
		return MSDOS_SB(sb)->options.quiet ? 0 : error;

	if (((attr->ia_valid & ATTR_UID) && 
	     (attr->ia_uid != MSDOS_SB(sb)->options.fs_uid)) ||
	    ((attr->ia_valid & ATTR_GID) && 
	     (attr->ia_gid != MSDOS_SB(sb)->options.fs_gid)) ||
	    ((attr->ia_valid & ATTR_MODE) &&
	     (attr->ia_mode & ~MSDOS_VALID_MODE)))
		error = -EPERM;

	if (error)
		return MSDOS_SB(sb)->options.quiet ? 0 : error;

	error = inode_setattr(inode, attr);
	if (error)
		return error;

	if (S_ISDIR(inode->i_mode))
		inode->i_mode |= S_IXUGO;

	inode->i_mode = ((inode->i_mode & S_IFMT) | ((((inode->i_mode & S_IRWXU
	    & ~MSDOS_SB(sb)->options.fs_umask) | S_IRUSR) >> 6)*S_IXUGO)) &
	    ~MSDOS_SB(sb)->options.fs_umask;
	return 0;
}
MODULE_LICENSE("GPL");